Multi-Directional Elastomeric Dampened Ball Joint Assembly

ABSTRACT

A method and apparatus for reducing a force. An apparatus comprises a multi-directional joint assembly and a damper associated with the multi-directional joint assembly. The multi-directional joint assembly has a first end and a second end. The first end and the second end move relative to each other. The damper is comprised of a number of elastomeric layers and a number of rigid layers interspersed with each other reducing at least one of a force and a moment.

BACKGROUND INFORMATION

1. Field

The present disclosure relates generally to structures and, inparticular, to structures carrying loads. Still more particularly, thepresent disclosure relates to a method and apparatus for carrying loadswhile allowing controlled displacement of the structures carrying theloads.

2. Background

With mechanical systems, different objects may be connected to eachother. For example, a bridge may have towers, parts of a deck,suspension cables, and other components that are connected to eachother. In some cases, the connection between objects may allow formovement, expansion, or contraction of the objects. The point ofconnection of two or more objects is a joint. In some cases, jointsconnecting two objects together may be multi-directional joints thatallow movement in more than one direction.

When objects are connected to each other, dampers may be used. A damperis a physical structure connected to the objects. When a load is carriedthrough the damper, the damper allows a controlled amount of deflectionin at least one direction which reduces any force applied in thatdirection. In other words, a damper may arrest movement in certaindirections but allow deflection and reduced loads in other directions.This process constrains relative motion between the objects in responseto applied loads and forces while reducing the forces carried throughthe system in the directions that are able to deflect.

A damper, used with a load bearing joint, may constrain the relativemotion between objects to only a few degrees of freedom. For example, ahydraulic damper, such as an automotive shock absorber, may be used toallow one-dimensional movement of a point along a line. In anotherexample, a cylindrical elastomeric bearing may accommodate rotationabout a fixed axis.

A damper may limit motion to certain degrees of freedom using a designthat reduces deflection to certain directions. For example, anelastomeric bearing is comprised of layers of a deformable elastomermaterial and layers of a rigid material. As used herein, “rigid”material is material that does not have deflection. The rigid layers maybe placed between elastomeric layers such that the rigid layers slidewith resistance relative to each other but the separation or compressionof the rigid layers is prevented by the stacking of the elastomericmaterial in thin layers between the rigid layers.

Different types of dampers are used in different situations, dependingon the desired degrees of freedom of the objects and the types of loadsto be applied to the objects. For example, an elastomeric bearing may beused between two parts of a deck in a bridge such that these parts mayexpand or contract in response to changes in temperature. As anotherexample, an elastomeric bearing may be used in a rotor assembly for ahelicopter to absorb energy from dynamic loads and vibrations from rotorblades.

The elastomeric bearing used in one situation may not function as wellas desired in another situation. For example, the loads and forcedirections that are encountered by an elastomeric bearing used in abridge may be very different from the loads and force directionsencountered by an elastomeric bearing used in a rotor assembly for ahelicopter. As a result, the desired geometry, quantity, and thicknessof layers within an elastomeric bearing for one application may differfrom the desired geometry, quantity, and thickness of layers for otherapplications.

Thus, as new applications using elastomeric bearings are implemented,new bearing designs are developed to provide a level of resistance thatreduces the amount of deflection to a level desired for the newapplication. Therefore, it would be desirable to have a method andapparatus that takes into account at least some of the issues discussedabove, as well as other possible issues.

SUMMARY

In one illustrative configuration, an apparatus comprises amulti-directional joint assembly and a damper. The multi-directionaljoint assembly has a first end and a second end. The first end and thesecond end move relative to each other. The damper is comprised of anumber of elastomeric layers and a number of rigid layers interspersedwith each other.

In another illustrative configuration, a multi-directional elastomericdampened ball joint assembly comprises a ball, a socket, and ahemispherical elastomeric bearing. The ball is associated with a firstend of the multi-directional elastomeric dampened ball joint assembly.The socket is associated with a second end of the multi-directionalelastomeric dampened ball joint assembly. The ball is moveably held in acavity in the socket. The hemispherical elastomeric bearing hasalternating rigid layers and elastomeric layers. The outer surface ofthe hemispherical elastomeric bearing is associated with an innersurface of an enclosure. The inner surface of the hemisphericalelastomeric bearing is associated with an outer surface of the socket.The hemispherical elastomeric bearing absorbs energy and reduces atleast one of a force and a moment applied to at least one of the firstend and the second end.

In yet another illustrative configuration, a method for reducing a forceis provided. At least one of a number of forces and a number of momentsis applied to at least one of a first end and a second end of amulti-directional joint assembly is received. The first end and thesecond end move relative to each other. A number of elastomeric layersin a damper associated with the multi-directional joint assembly aredeformed. The damper comprises the number of elastomeric layers and anumber of rigid layers interspersed with each other.

The features and functions can be achieved independently in variousconfigurations of the present disclosure or may be combined in yet otherconfigurations in which further details can be seen with reference tothe following description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features believed characteristic of the illustrativeconfigurations are set forth in the appended claims. The illustrativeconfigurations, however, as well as a preferred mode of use, furtherobjectives and features thereof, will best be understood by reference tothe following detailed description of an illustrative configuration ofthe present disclosure when read in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is an illustration of a load environment in accordance with anillustrative configuration;

FIG. 2 is an illustration of a block diagram of a joint system inaccordance with an illustrative configuration;

FIG. 3 is a detailed illustration of a joint system in accordance withan illustrative configuration;

FIG. 4 is an illustration of a multi-directional joint assembly inaccordance with an illustrative configuration;

FIG. 5 is another illustration of a multi-directional joint assembly inaccordance with an illustrative configuration;

FIG. 6 is an illustration of an exploded view of a multi-directionaljoint assembly in accordance with an illustrative configuration;

FIG. 7 is an illustration of a cross-sectional view of amulti-directional joint assembly in accordance with an illustrativeconfiguration;

FIG. 8 is an exposed isometric view of a multi-directional jointassembly in accordance with an illustrative configuration;

FIG. 9 is an illustration of a torsional force applied to amulti-directional joint assembly in accordance with an illustrativeconfiguration;

FIG. 10 is another illustration of a torsional force applied to amulti-directional joint assembly in accordance with an illustrativeconfiguration;

FIG. 11 is an illustration of a cross-sectional view of a bending forceapplied to a multi-directional joint assembly in accordance with anillustrative configuration;

FIG. 12 is another illustration of a cross-sectional view of a bendingforce applied to a multi-directional joint assembly in accordance withan illustrative configuration;

FIG. 13 is a detailed illustration of layers in an elastomeric bearingin accordance with an illustrative configuration;

FIG. 14 is an illustration of layers in an elastomeric bearing in aloaded condition in accordance with an illustrative configuration;

FIG. 15 is an illustration of a flowchart of a process for absorbing aforce in accordance with an illustrative configuration; and

FIG. 16 is another illustration of a flowchart of a process forabsorbing a force in accordance with an illustrative configuration.

DETAILED DESCRIPTION

The illustrative configurations recognize and take into account one ormore different considerations. For example, the illustrativeconfigurations recognize and take into account that in some cases, itmay be desirable to maintain a relative position between two objectswithin desired tolerances.

The illustrative configurations recognize and take into account that aspacing structure such as a beam may be used to maintain a desireddistance between the two objects. The desired distance may be a requireddistance for the operation of the two objects or may be based on otherconsiderations, depending on the particular implementation. The beam maybe used to connect two objects to each other to ensure the requireddistance between the two objects is maintained while allowing relativemovements within desired tolerances. For example, the beam may beconnected to the objects such that relative movement up, down, left, andright occurs within desired tolerances. Similarly, the connection mayalso allow rotational movement within desired tolerances. Rotationalmovement is also known as torsional movement in these illustrativeexamples.

The illustrative configurations also recognize and take into accountthat a joint may be designed to limit degrees of freedom with respect tothe movement of the objects relative to each other. When the type ofmovement that is provided, limited, or provided and limited includesangular and rotational movement, the joint may take the form of amulti-directional joint assembly. When the type of movement that isprovided, limited, or provided and limited includes angular movementonly, the joint may take the form of a U-joint.

Additionally, the illustrative configurations recognize and take intoaccount that movement of the two objects relative to each other mayresult in different types of forces being applied to the two objectsconnected to each other with a beam. For example, these forces mayinclude one or more of a torsional force, a bending force, and a normalforce. In these illustrative examples, a normal force may be a tensionforce or a compression force.

The illustrative configurations also recognize and take into accountthat deflection may be desired to reduce loads at the joint between thebeam and the objects, where bending forces are highest. This type ofmovement may be facilitated using a multi-directional joint assemblywith a damper. This damper deforms and reduces the load. In particular,the joints between objects may include a damper in the form of anelastomeric bearing.

Moreover, the illustrative configurations recognize and take intoaccount that elastomeric bearings are well suited as dampers when loadsoccur simultaneously in different situations. In this case, joints maytake the form of ball joints. A ball joint with an elastomeric bearingmay be used to carry normal force through the ball joint to maintain adesired distance between objects while still allowing bending ortorsional deflection within desired tolerances.

The illustrative configurations also recognize and take into accountthat an elastomeric bearing includes several layers of an elastomer thatdeform under a load. This deformation results in relative movement ofthe objects attached to opposite sides of the elastomeric bearing. Theelastomer is a polymeric material. When a load is applied to thepolymeric material, the polymeric material deforms in shear. When theload is removed, the polymeric material returns to substantially itsoriginal shape. In other words, the polymeric material returns to itsoriginal shape within selected tolerances. As used herein, “shear”stress is stress which is applied parallel or tangential to a face of amaterial.

With reference now to the figures and, in particular, with reference toFIG. 1, an illustration of a load environment is depicted in accordancewith an illustrative configuration. As depicted, load environment 100includes helicopter 102, helicopter 104, and helicopter 106. Helicopter102, helicopter 104, and helicopter 106 move object 108. Object 108 maytake various forms. For example, object 108 may be a container, avehicle, a payload, or some other suitable type of object.

As depicted, object 108 is connected to helicopter 102, helicopter 104,and helicopter 106 by the line 110, line 112, and line 114,respectively. In this example, the weight of object 108 may pullhelicopter 102, helicopter 104, and helicopter 106 toward each otherduring flight. As a result, spacing is maintained between helicopter102, helicopter 104, and helicopter 106 using beam 116, beam 118, andbeam 120. In these illustrative examples, beam 116 is connected tohelicopter 102 and helicopter 106, beam 118 is connected to helicopter102 and helicopter 104, and beam 120 is connected to helicopter 104 andhelicopter 106.

The connections of beam 116, beam 118, and beam 120 to helicopter 102,helicopter 104, and helicopter 106 may be made using joint system 122,joint system 124, and joint system 126. Each joint system comprises anumber of joint assemblies. In these illustrative examples, a jointsystem may comprise two joint assemblies with each joint assemblyconnecting a helicopter to a beam. Within each joint assembly, amultidirectional joint and a damper may be present.

As depicted, joint system 122 is associated with helicopter 102, beam116, and beam 118. In other words, a first joint in joint system 122connects helicopter 102 with beam 116 and a second joint connectshelicopter 102 with beam 118. Similarly, joint system 124 is associatedwith helicopter 104, beam 118, and beam 120. Joint system 126 isassociated with helicopter 106, beam 120, and beam 116.

When one component is “associated” with another component, theassociation is a physical connection in these depicted examples. Forexample, a first component, a joint in joint system 122, may beconsidered to be associated with a second component, helicopter 102, bybeing secured to the second component, bonded to the second component,mounted to the second component, welded to the second component,fastened to the second component, and/or connected to the secondcomponent in some other suitable manner. The first component also may beconnected to the second component using a third component. The firstcomponent may also be considered to be associated with the secondcomponent by being formed as part of and/or as an extension of thesecond component.

With this configuration of helicopter 102, helicopter 104, andhelicopter 106, many different forces may occur while carrying object108. In this depicted example, the forces include horizontal forces thatpull helicopter 102, helicopter 104, and helicopter 106 toward eachother. These forces may be reacted by compressive loads carried throughbeam 116, beam 118, and beam 120. For example, a force pullinghelicopter 102 toward helicopter 104 results in a compressive load beingreacted through beam 118 in these illustrative examples.

The compressive forces within one or more of beam 116, beam 118, andbeam 120 also may be introduced into the airframe of one or more ofhelicopter 102, helicopter 104, and helicopter 106 using variousmechanisms. For example, a fixed joint, a flexible beam, a hydraulicactuator, a multi-directional joint, or other suitable types ofmechanisms may be used.

In one example, joint system 122, joint system 124, and joint system 126may be fixed joint systems. This type of joint system, however, may notprovide a desired amount of movement between helicopter 102, helicopter104, and helicopter 106 relative to each other. Without relativemovement between helicopter 102, helicopter 104, and helicopter 106, thefixed joint system will induce bending loads, torsional loads, or bothto be reacted at joint system 122, joint system 124, and joint system126. These loads may be undesirable in these illustrative examples.

In another example, beam 116, beam 118, and beam 120 may be designed toallow for deflection. This type of beam design, however, limits thedeflection properties of the system to the material and geometryselected for beam 116, beam 118, and beam 120. In other words, thematerial and geometry selected for beam 116, beam 118, and beam 120determines the maximum amount of deflection possible for the system.Further, designing beam 116, beam 118, and beam 120 to allow deflectionmay compromise the compressive load capability of the beams, increasebeam weight, or both. Additionally, the selection of a flexible materialfor beam 116, beam 118, and beam 120 does not directly address bendingloads at the joints where the bending force is highest. Thus, designingbeam 116, beam 118, and beam 120 to allow for deflection may beundesired in these illustrative examples.

In yet another example, hydraulic actuators may be used in joint system122, joint system 124, and joint system 126. Hydraulic actuators,however, may not provide movement in as many directions as desired. Forexample, because hydraulic actuators are linear acting, joint system122, joint system 124, and joint system 126 would require additionalsupport structures with multiple hydraulic actuators to accommodatevarious degrees of freedom. As a result, the use of multiple hydraulicactuators to provide movement in a desired number of directions mayincrease system complexity and cost.

In this illustrative example, joint system 122, joint system 124, andjoint system 126 each have joints that allow for movement in a desirednumber of directions. An illustrative configuration may be implementedin joint system 122, joint system 124, and joint system 126. Inparticular, joint system 122, joint system 124, and joint system 126 mayemploy multi-directional joints such as ball joints. A more detailedillustration of joint system 122 in section 128 is shown and describedwith respect to FIG. 3, below.

In these illustrative examples, an illustrative configuration may beimplemented in one or more of joint system 122, joint system 124, andjoint system 126 to maintain the movement of a beam and a helicopterrelative to each other within a desired tolerance. For example, anillustrative configuration may be implemented in joint system 122 tomaintain movement of beam 116 relative to helicopter 102 within adesired tolerance of five feet. Of course, the desired tolerance may beany distance, depending on the particular implementation.

Further, an illustrative configuration may be implemented in jointsystem 122, joint system 124, and joint system 126 to reduce a force,absorb the force, dampen the force, or some combination thereof withrespect to forces that may be applied to joint system 122, joint system124, and joint system 126 during operation of helicopter 102, helicopter104, and helicopter 106. Moreover, an illustrative configuration may beimplemented in joint system 122, joint system 124, and joint system 126to reduce a moment, absorb the moment, dampen the moment, or somecombination thereof with respect to moments that may be applied to jointsystem 122, joint system 124, and joint system 126. As used herein a“moment” is a force acting over a distance.

For example, an illustrative configuration may include an apparatus thatmay be implemented in at least one of joint system 122, joint system124, and joint system 126. In one or more illustrative configurations,an apparatus comprises a multi-directional joint assembly and a damper.The multi-directional joint assembly has a first end and a second end.The first end and the second end move relative to each other. The damperis associated with the multi-directional joint assembly. The damper iscomprised of a number of rigid layers and a number of elastomeric layersinterspersed with each other. As used herein, a “number of,” when usedwith reference to items, means one or more items. For example, a numberof rigid layers is one or more rigid layers.

Turning next to FIG. 2, an illustration of a block diagram of a jointsystem is depicted in accordance with an illustrative configuration.Joint system 200 is an example of a joint system that may be used toimplement at least one of joint system 122, joint system 124, and jointsystem 126 in load environment 100 in FIG. 1.

As used herein, the phrase “at least one of,” when used with a list ofitems, means different combinations of one or more of the listed itemsmay be used and only one of each item in the list may be needed. Forexample, “at least one of item A, item B, and item C” may include,without limitation, item A or item A and item B. This example also mayinclude item A, item B, and item C or item B and item C. In otherexamples, “at least one of” may be, for example, without limitation, twoof item A, one of item B, and ten of item C; four of item B and seven ofitem C; and other suitable combinations.

As depicted, joint system 200 includes number of joint assemblies 201.Multi-directional joint assembly 202 is a joint assembly in number ofjoint assemblies 201 in which an illustrative configuration may beimplemented. In particular, multi-directional joint assembly 202 mayinclude multi-directional joint 204 and damper 215. In theseillustrative examples, multi-directional joint 204 may be a ball joint.Of course, multi-directional joint assembly 202 may comprise other typesof multi-directional joints other than a ball joint, depending on theparticular implementation.

In this illustrative example, multi-directional joint assembly 202 hasfirst end 206 and second end 208. First end 206 is connected to firstobject 210, while second end 208 is connected to second object 212. Forexample, first end 206 may be connected to beam 116 and second end 208may be connected to a rotorcraft such as helicopter 102 in FIG. 1.

As depicted, first object 210 and second object 212 may take differentforms depending on the particular implementation. In one illustrativeexample, first object 210 may be beam 116, while second object 212 maybe helicopter 102.

As used herein, a first component that is “connected to” a secondcomponent means that the first component can be connected directly orindirectly to the second component. In other words, additionalcomponents may be present between the first component and the secondcomponent. The first component is considered to be indirectly connectedto the second component when one or more additional components arepresent between the two components. When the first component is directlyconnected to the second component, no additional components are presentbetween the two components.

As depicted, multi-directional joint 204 has ball 213 and socket 214.First end 206 of multi-directional joint assembly 202 is associated withball 213 of multi-directional joint 204 and second end 208 ofmulti-directional joint assembly 202 is associated with socket 214 ofmulti-directional joint 204. As depicted, ball 213 and socket 214 arephysical structures. Socket 214 holds ball 213.

Further, multi-directional joint assembly 202 also includes damper 215within interior 216 of multi-directional joint assembly 202. In thisillustrative example, damper 215 is elastomeric structure 218. Inparticular, damper 215 may be elastomeric bearing 220.

Still more particularly, multi-directional joint assembly 202 may takethe form of multi-directional elastomeric dampened ball joint assembly222. In this form, multi-directional elastomeric dampened ball jointassembly 222 may aid in the absorption of number of forces 223. Numberof forces 223 may include, for example, at least one of a torsionalforce, a compressive force, a bending force, a tension force, and othersuitable types of forces. In this example, multi-directional elastomericdampened ball joint assembly 222 may dampen number of forces 223. Thisdampening may include reducing vibrations in some instances.

In this illustrative example, damper 215 is comprised of layers 224. Inparticular, layers 224 may include number of elastomeric layers 226 andnumber of rigid layers 228.

In the illustrative example, number of elastomeric layers 226 and numberof rigid layers 228 are interspersed with each other. In other words,layers 224 may alternate between an elastomeric layer and a rigid layer.In yet another illustrative example, layers 224 may have two elastomericlayers and three rigid layers. The manner in which layers 224 alternatebetween different types of layers may vary depending on the particularimplementation.

An elastomeric layer in number of elastomeric layers 226 is a layer thatdeforms in response to number of loads 230. Number of loads 230 may beinput loads 231. As depicted, number of loads 230 may be a force appliedto damper 215 from other components in multi-directional joint assembly202.

When number of loads 230 is reduced or removed to a sufficient level,the elastomeric layer in number of elastomeric layers 226 maysubstantially return to its original shape. In other words, theelastomeric layer in number of elastomeric layers 226 may return to itsoriginal shape within selected tolerances.

In these depicted examples, an elastomeric layer may be, for example, apolymer. The polymer may have a viscoelasticity that has a desiredYoung's modulus and a desired yield strain. The desired Young's modulusmay be low and the desired yield strain may be high compared to othermaterials in damper 215 such as a rigid layer in number of rigid layers228.

In these illustrative examples, number of elastomeric layers 226 may becomprised of a number of materials with a desired viscoelasticity. Thenumber of materials may be selected from at least one of neoprene,rubber, an elastic polymer, a thermoplastic elastomer, syntheticpolyisoprene, polybutadiene, ethylene-vinyl acetate, chlorosulfonatedpolyethylene, and other suitable materials.

A rigid layer may not have the same properties found in an elastomericlayer. A rigid layer is configured with a low Young's modulus to forcethe deflection to take place in elastomeric layers only. By stackingalternating rigid layers and elastomeric layers, material deformation ofelastomeric layers in response to normal forces is arrested as a resultof the neighboring rigid layers which limit flow of deformed material.As a result, deformation occurs in response to shear loads only sincedeflection in response to normal forces is arrested by rigid layers.

In these illustrative examples, number of rigid layers 228 also may becomprised of a number of materials. The number of materials selected fornumber of rigid layers 228 may be selected from a metal such as, forexample, without limitation, aluminum, steel, titanium, or othersuitable materials.

The thicknesses used for number of elastomeric layers 226 and number ofrigid layers 228 in layers 224 may vary depending on the amount ofelastomeric bearing movement that may be desired for a given input load.In other words, if a larger amount of movement for elastomeric bearing220 is desired, an increased quantity, thickness, or both for number ofelastomeric layers 226 may be used. Conversely, if little movement ofelastomeric bearing 220 is desired, a decreased quantity, thickness, orboth for number of elastomeric layers 226 may be used. Increasing ordecreasing the Young's modulus of the elastomeric material will alsoincrease or decrease the amount of deflection for a given load.

Further, different layers may have different thicknesses within numberof elastomeric layers 226, depending on the desired movement ofelastomeric bearing 220. In a similar fashion, the number of rigidlayers 228 also may have different thicknesses. These thicknesses may beselected such that number of elastomeric layers 226 and number of rigidlayers 228 perform as desired.

In these illustrative examples, number of loads 230 may occur inresponse to at least one of number of forces 223 and number of moments225 being applied to at least one of first end 206 and second end 208 ofmulti-directional joint assembly 202. Number of forces 223 may be asingle force or may be a combination of forces that may be applied toone or both of first end 206 and second end 208. In these illustrativeexamples, number of forces 223 may include at least one of a normalforce, a reaction force, a portion force, a bending force, and othertypes of forces. Number of moments 225 may include at least one oftorsion, a bending moment, and other types of moments.

In this example, damper 215 carries bending and torsional loads anddeflects in these directions. Normal loads from structures connected tomulti-directional joint assembly 202 are reacted throughmulti-directional joint 204.

As depicted in these illustrative examples, damper 215 may absorb energyfrom number of forces 223 and number of moments 225 applied tomulti-directional joint assembly 202. For example, damper 215 absorbsenergy from bending and torsional complements comprising number of loads230. The absorption of initial energy 234 in the deformation of numberof elastomeric layers 226 results in heat 236 being released. In otherwords, number of forces 223 causing number of loads 230 may be reducedby absorbing initial energy 234 in the form of deformation 237 of numberof elastomeric layers 226 and releasing heat 236 in these illustrativeexamples.

Output loads 235 are then carried through first end 206 into firstobject 210 and through second end 208 into second object 212. Becauseinitial energy 234 is absorbed by number of elastomeric layers 226,output loads 235 are less than input loads 231 in these illustrativeexamples. In other words, output loads 235 are reduced loads. In thismanner, an illustrative configuration may provide a desired level ofmovement of first object 210 and second object 212 relative to eachother while preventing undesired movement of first object 210, secondobject 212, or both.

The illustration of joint system 200 in FIG. 2 is not meant to implyphysical or architectural limitations to the manner in which anillustrative configuration may be implemented. Other components inaddition to or in place of the ones illustrated may be used. Somecomponents may be unnecessary. Also, the blocks are presented toillustrate some functional components. One or more of these blocks maybe combined, divided, or combined and divided into different blocks whenimplemented in an illustrative configuration.

For example, additional joint assemblies may be present in addition tomulti-directional joint assembly 202. In still other illustrativeexamples, an additional structure in addition to or in place of damper215 also may be present within multi-directional joint assembly 202.This additional structure also may absorb loads such as number of loads230 and generate heat 236 from initial energy 234 in number of loads 230such that multi-directional joint 204 performs as desired.

With reference now to FIG. 3, a detailed illustration of a joint systemis depicted in accordance with an illustrative configuration. In thisfigure, a more detailed illustration of section 128 in FIG. 1 is shown.

As depicted, joint system 122 includes multi-directional joint assembly300 and multi-directional joint assembly 302. Multi-directional jointassembly 300 and multi-directional joint assembly 302 are examples ofphysical implementations for multi-directional joint assembly 202 withmulti-directional joint 204 and damper 215 shown in block form in FIG.2. A multi-directional joint and a damper (not shown) are located withineach of multi-directional joint assembly 300 and multi-directional jointassembly 302 in these depicted examples.

In this illustrative example, multi-directional joint assembly 300 hasfirst end 304 and second end 306. First end 304 is associated with beam116, and second end 306 is associated with helicopter 102.Multi-directional joint assembly 302 has first end 308 and second end310. First end 308 is associated with beam 118, and second end 310 isassociated with helicopter 102.

As depicted, first end 304, second end 306, first end 308, and secondend 310 are physical structures. First end 304, second end 306, firstend 308, and second end 310 provide locations on multi-directional jointassembly 300 and multi-directional joint assembly 302 that may beassociated with other structures.

In this illustration, beam 116 and beam 118 are shown in phantom. Thisview of beam 116 and beam 118 is provided to illustrate the connectionof first end 304 with beam 116 and first end 308 with beam 118.

In these illustrative examples, different forces may occur that applyloads to multi-directional joint assembly 300 or multi-directional jointassembly 302 during the operation of the helicopters carrying object 108in FIG. 1. For example, a force may be applied in the direction of arrow314, arrow 316, and arrow 320. Arrow 314 represents a bending force. Asanother example, arrow 316 represents a torsional force. The torsionalforce represented by arrow 316 is applied rotationally about axis 318 inthis illustrative example. As yet another example, arrow 320 representsan example of a compressive force. This compression force may be appliedalong axis 318.

This illustration of the different types of forces is depicted toprovide an example of some of the types of forces that may be applied toa multi-directional joint assembly in joint system 122. Of course, othertypes of forces may be applied in addition to or in combination with theforces illustrated in this example.

Turning now to FIG. 4, an illustration of a multi-directional jointassembly is depicted in accordance with an illustrative configuration.In this example, a more detailed illustration of multi-directional jointassembly 300 in FIG. 3 is shown in a perspective view.

In this illustration, multi-directional joint assembly 300 is shownwithout the components that may be associated with or connected to firstend 304 and second end 306 of multi-directional joint assembly 300.First end 304 and second end 306 move relative to each other in bending.This movement may also include torsional movement.

In FIG. 5, another illustration of a multi-directional joint assembly isdepicted in accordance with an illustrative configuration. In thisfigure, another perspective view of multi-directional joint assembly 300is shown from second end 306.

With reference now to FIG. 6, an illustration of an exploded view of amulti-directional joint assembly is depicted in accordance with anillustrative configuration. As can be seen in this exploded view,multi-directional joint assembly 300 includes a number of differentcomponents. As depicted, multi-directional joint assembly 300 includesenclosure 600. In this particular example, enclosure 600 is comprised offirst portion 603 and second portion 605. Multi-directional jointassembly 300 also includes ring 601, ball 602, socket 604, andelastomeric bearing 606. Ring 601, ball 602, and socket 604 comprisemulti-directional joint 607. Multi-directional joint 607 may be oneexample of an implementation for multi-directional joint 204 shown inblock form in FIG. 2.

First portion 603 and second portion 605 of enclosure 600 are physicalstructures that hold ball 602, socket 604, and elastomeric bearing 606within interior 610 of enclosure 600. Second portion 605 may beconnected to first portion 603 of enclosure 600 of multi-directionaljoint assembly 300.

As depicted, ball 602 is a physical structure that is associated withfirst portion 603 of enclosure 600. In these illustrative examples, ball602 may be formed as part of first portion 603 of enclosure 600 or maybe connected to first portion 603 of enclosure 600 within interior 610of first portion 603 of enclosure 600. Ball 602 has a shape of a spherein this illustrative example.

In this example, socket 604 receives and hold ball 602. Ring 601 may beconnected to socket 604 to retain ball 602 within socket 604. Ring 601may be connected to socket 604 by being bonded, welded, or otherwiseconnected to socket 604.

Elastomeric bearing 606 takes a hemispherical form in this illustrativeexample. In these examples, a hemispherical elastomeric bearing is anelastomeric bearing that is allows movement in multiple degrees offreedom. In other words, elastomeric bearing 606 allows movement in morethan one direction.

As illustrated, multi-directional joint assembly 300 is rigid withrespect to normal forces, such as compression and tension loads, reactedalong axis 318. However, elastomeric bearing 606 reacts bending andtorsional forces and enables load reduction in these directions throughdeflection in bending and torsion. In other words, the multi-directionaljoint assembly is rigid when reacting compression and tension loadsintroduced by a beam, but allows the beam to bend up, down, left, right,rotate, or some combination thereof relative to an airframe. Thisrelative motion will be reduced to some amount of movement by theconfiguration of layers within elastomeric bearing 606. This reductionin the movement may be referred to as a limit to the movement of thebeam.

As illustrated, elastomeric bearing 606 has opening 616 and secondportion 605 of enclosure 600 has opening 618. Opening 616 and opening618 allows second end 306 to extend through opening 616 and opening 618.As depicted, elongate member 620 associates second end 306 with secondportion 605 of enclosure 600. Opening 616 and opening 618 are alsoallows second end 306 to move in a number of different directions.

In this illustrative example, first portion 603, ball 602, socket 604,second portion 605, and ring 601 may be comprised of a material selectedfrom at least one of a metal, a plastic, a polycarbonate, aluminum,copper, titanium, steel, and other suitable materials. The materialselected for first portion 603, ball 602, socket 604, second portion605, and ring 601 may be one that may withstand the forces, environment,and other conditions that multi-directional joint assembly 300 may beexposed to during use of multi-directional joint assembly 300. Differentcomponents may be comprised of different materials.

In this particular example, the elastomeric layers in elastomericbearing 606 are formed using neoprene. Of course, the material selectedfor the elastomeric layers may be any material that provides a desiredlevel of viscoelasticity.

Turning now to FIG. 7, an illustration of a cross-sectional view of amulti-directional joint assembly is depicted in accordance with anillustrative configuration. In this figure, a cross-sectional view ofmulti-directional joint assembly 300 is shown taken along lines 7-7 inFIG. 4.

In this cross-sectional view, elongate member 700 extends from ball 602to first end 304. Additionally, ball 602 can be seen as being retainedwithin cavity 702 of socket 604 by ring 601.

As depicted, elastomeric bearing 606 is comprised of layers 704. Layers704 are an example of number of elastomeric layers 226 shown in blockform in FIG. 2.

As can be seen in section 705, layers 704 alternate between elastomericlayers and rigid layers. In this example, elastomeric layer 706 islocated between rigid layer 708 and second portion 605 of enclosure 600.In particular, elastomeric layer 706 may be associated with innersurface 707 of second portion 605. Second portion 605 may function as arigid layer and may be considered a rigid layer in this particularexample. As another example, elastomeric layer 712 is located betweenrigid layer 714 and rigid layer 716 in layers 704. Rigid layer 714 isassociated with outer surface 717 of socket 604. In other illustrativeexamples, some portions of layers 704 may not be associated with eachother or may not be associated with second portion 605 of enclosure 600,socket 604, or both, depending on the particular implementation.

In this illustrative example, the different layers in layers 704 areassociated with each other such that layers 704 do not slide relative toeach other. In other words, a layer in layers 704 will not slide acrossthe surface of another layer in layers 704 or separate from other layersin layers 704 in some other manner. Layers within layers 704 may bebonded to each other or secured to one another in some other suitablemanner.

Turning now to FIG. 8, an exposed isometric view of a multi-directionaljoint assembly is depicted in accordance with an illustrativeconfiguration. An exposed isometric view of multi-directional jointassembly 300 is shown in a static state. In this state, no bending ortorsional forces are applied to multi-directional joint assembly 300.

In FIG. 9, an illustration of a torsional force applied to amulti-directional joint assembly is depicted in accordance with anillustrative configuration. As depicted, torsional force 900 is appliedto multi-directional joint assembly 300. In this example, torsionalforce 900 is a force in a direction about axis 318 that extendscentrally through multi-directional joint assembly 300. Torsional force900 is applied in a clockwise direction at first end 304 ofmulti-directional joint assembly 300 in this illustrative example.Torsional force 900 may cause ball 602 to rotate relative to socket 604about axis 318.

Torsional force 900 is reacted by elastomeric bearing 606. Inparticular, elastomeric bearing 606 incurs a deflection in rotation thatabsorbs energy and reduces the torsional load carried between first end304 and second end 306 of multi-directional joint assembly 300. Thisload will occur when the first end 304 and second end 306 rotaterelative to each other along axis 318. At least a portion of this energymay be converted into heat in this illustrative example.

When torsional force 900 is no longer applied at first end 304,elastomeric bearing 606 may substantially return to the original stateas illustrated in FIG. 8. In this manner, elastomeric bearing 606absorbs energy from torsional force 900 while multi-directional jointassembly 300 remains rigid along axis 318 to maintain a desired relativedistance between a first object associated with first end 304 and asecond object associated with second end 306 of multi-directional jointassembly 300. In this particular example, energy is not absorbed inother directions such as bending.

With reference next to FIG. 10, another illustration of a torsionalforce applied to a multi-directional joint assembly is depicted inaccordance with an illustrative configuration. In this example,torsional force 1000 is applied at first end 304 of multi-directionaljoint assembly 300. Torsional force 1000 is applied in an oppositedirection to torsional force 900 in FIG. 9. In this depicted example,torsional force 1000 is applied in a counterclockwise direction aboutaxis 318.

The application of torsional force 1000 also may cause a load to beapplied on elastomeric bearing 606 that causes elastomeric bearing 606to deform. This deformation also absorbs energy from the load placed onelastomeric bearing 606 through deformation that results from reactingtorsional force 1000. When torsional force 1000 is no longer applied atfirst end 304, elastomeric bearing 606 may substantially return to itsoriginal state as illustrated in FIG. 8.

With reference now to FIG. 11, an illustration of a cross-sectional viewof a bending force applied to a multi-directional joint assembly isdepicted in accordance with an illustrative configuration. In thiscross-sectional view taken along lines 7-7 in FIG. 4, bending force 1100is applied at first end 304 of multi-directional joint assembly 300. Inthis illustrative example, bending force 1100 is applied relative toaxis 318. In particular, bending force 1100 may be perpendicular to orat some other angle relative to axis 318.

Bending force 1100 results in a load being reacted by elastomericbearing 606. With a beam type configuration as used in this illustrativeexample, the bending load component is greater than the normal loads ortorsional loads. Reaction of this load causes a deformation ofelastomeric bearing 606. This load occurs where first end 304 rotatesrelative to second end 306 at any axis perpendicular to axis 318. Sincethe outer surface of elastomeric bearing 606 is attached to secondportion 605 of enclosure 600 and the inner surface of elastomericbearing 606 is attached to socket 604, any bending loads applied to thejoint system are reacted by elastomeric bearing 606. Energy from theload causing deformation by means of bending force 1100 may be convertedinto heat in elastomeric bearing 606.

When bending force 1100 is no longer applied at first end 304, a load isno longer applied to elastomeric bearing 606. As a result, elastomericbearing 606 may return to substantially its original state as shown inFIG. 8.

Next, in FIG. 12, another illustration of a cross-sectional view of abending force applied to a multi-directional joint assembly is depictedin accordance with an illustrative configuration. In thiscross-sectional view taken along lines 7-7 in FIG. 4, bending force 1200is applied at first end 304. Bending force 1200 is opposite to bendingforce 1100 in FIG. 11 relative to axis 318.

In these illustrative examples, the application of bending force 1200applies a load to elastomeric bearing 606 that causes the deformation ofelastomeric bearing 606. Energy from bending force 1200 is absorbed bydeforming elastomeric bearing 606. Some of this energy may also beconverted to heat as a result of deforming elastomeric bearing 606. Whenbending force 1200 is removed, elastomeric bearing 606 may substantiallyreturn to its original state as illustrated in FIG. 8.

In FIG. 13, a detailed illustration of layers in an elastomeric bearingis depicted in accordance with an illustrative configuration. A moredetailed illustration of layers 704 in section 705 from FIG. 7 is shown.In particular, elastomeric layer 712 is depicted between rigid layer 714and rigid layer 716. Layers 704 are depicted in an unloaded state.

With reference next to FIG. 14, an illustration of layers in anelastomeric bearing in a loaded condition is depicted in accordance withan illustrative configuration. As seen in this figure, layers 704 areshown as deformed in response to force 1400 being applied to one end ofmulti-directional joint assembly 300. Force 1400 causes the load todeform elastomeric layers in layers 704 in elastomeric bearing 606.

As can be seen, the rigid layers in layers 704 within elastomericbearing 606 have moved relative to each other. This movement isfacilitated by deformation of the elastomeric layers in shear reactingto force 1400.

In particular, rigid layer 714 and rigid layer 716 have moved relativeto each other because elastomeric layer 712 has deformed in shear.Similarly, the other rigid layers move relative to each other due todeformation in the other elastomeric layers in layers 704. When force1400 is removed, layers 704 may return to the state as shown in FIG. 13.

In this manner, a first object associated with first end 304 ofmulti-directional joint assembly 300 and a second object associated withsecond end 306 of multi-directional joint assembly 300 may move relativeto each other. However, this movement is limited by the configuration oflayers 704 in elastomeric bearing 606.

The illustration of multi-directional joint assembly 300 in FIGS. 3-14is provided only for purposes of illustrating one manner in whichmulti-directional joint 204 shown in block form in FIG. 2 may beimplemented. These illustrations of multi-directional joint assembly 300are not meant to imply limitations to the manner in which differentillustrative configurations may be implemented.

For example, although the different elastomeric layers in layers 704 inelastomeric bearing 606 are shown as having the same thickness, otherthicknesses may be present such that different layers within theelastomeric layers may have different thicknesses. In a similar fashion,different rigid layers in layers 704 of elastomeric bearing 606 also mayhave different thicknesses. Further, although 18 layers are shown inlayers 704, other numbers of elastomeric layers and rigid layers may bepresent in elastomeric bearing 606, depending on the desiredfunctionality for elastomeric bearing 606.

The different components shown in FIG. 1 and FIGS. 3-14 may be combinedwith components in FIG. 2, used with components in FIG. 2, or acombination of the two. Additionally, some of the components in FIG. 1and FIGS. 3-14 may be illustrative examples of how components shown inblock form in FIG. 2 can be implemented as physical structures.

With reference now to FIG. 15, an illustration of flowchart of a processfor absorbing a force is depicted in accordance with an illustrativeconfiguration. The process illustrated in FIG. 15 may be implemented inload environment 100 in FIG. 1. In particular, the processes may beimplemented using joint system 200 in FIG. 2.

At least one of a number of forces and a number of moments is receivedin which the number of forces and the number of moments are applied toat least one of a first end and a second end of a multi-directionaljoint assembly (operation 1500). The first end and the second end moverelative to each other in the multi-directional joint assemblies. Thismovement may occur as a result of forces and/or moments applied to atleast one of the first end and the second end. A number of elastomericlayers and a structure in the joint are deformed (operation 1502). Thenumber of elastomeric layers is located in a structure in themulti-directional joint assembly. The number of elastomeric layers isinterspersed with a number of rigid layers within the structure.

The process absorbs energy from the at least one of the number of forcesand the number of moments through the deformation of the number ofelastomeric layers (operation 1504) with the process terminatingthereafter. This absorption of energy may be released as heat in theseillustrative examples.

With reference now to FIG. 16, another illustration of a flowchart of aprocess for absorbing a force is depicted in accordance with anillustrative configuration. The process illustrated in FIG. 16 may beimplemented in load environment 100 in FIG. 1. In particular, theprocesses may be implemented using joint system 200 in FIG. 2.

In this example, joint system 200 is used to maintain a fixed distancebetween a first object and a second object. Further, joint system 200allows some amount of relative movement between the first object and thesecond object. The process begins by imposing at least one of forces andmoments on the first object that are different than the forces and themoments imposed on the second object (operation 1600). This first objectmay be first object 210 in FIG. 2 and may be an example of an objectsuch as helicopter 102 in FIG. 1. This second object may be secondobject 212 in FIG. 2 and may be a beam such as beam 116 in FIG. 1.

A combination of the forces and the moments is applied to the jointsystem connecting the first object and the second object (operation1602). In these depicted examples, the difference in forces imposed onthe first object and the second object causes a combination of normal,bending, and torsional forces to be applied to the joint system.Further, torsion, a bending moment, or other types of moments may beapplied to the joint system. These forces and moments result in a numberof loads being applied to the joint system.

As illustrated, the joint system is comprised of a third object thatconnects the first and second objects. For example, beam 116 may connecthelicopter 102 to helicopter 106. In this example, each end of the thirdobject features a multi-directional joint assembly with an elastomericbearing. In other words, one multi-directional joint assembly connectsthe first object to the third object and a second multi-directionaljoint assembly connects the second object to the third object. Forexample, a first multi-directional joint assembly connects helicopter102 with beam 116 and a second multi-directional joint assembly connectsbeam 116 with helicopter 106 in these illustrative examples.

Next, a combination of normal, bending, and torsional loads are inducedat the multi-directional joint assemblies between objects (operation1604). The normal load is reacted rigidly by the multi-directional jointassembly while the bending and torsional loads are reacted by theelastomeric bearing in the joint system such that the elastomericbearing may deform. In this illustrative example, the combination ofnormal, bending, and torsional loads may be a result of the displacementof the first object, second object, third object, or some combinationthereof. As a result, the normal loads are carried directly intohelicopter 102 and helicopter 106 via multi-directional joint assembliesat the ends of beam 116, while the bending and torsional loads arepassed through the elastomeric bearings surrounding themulti-directional joint assemblies between these objects.

Next, elastomeric layers in the elastomeric bearing are deformed(operation 1606). In this illustrative example, the bending andtorsional loads reacted by the elastomeric bearing cause the deformationin the elastomeric layers. These elastomeric layers may be elastomericlayers within layers 704 of elastomeric bearing 606 in FIG. 7. Theseelastomeric layers deform in shear and cause the rigid layers withinlayers 704 to move relative to each other. The elastomeric layers maydeform a limited amount in response to the loads applied. For example,the elastomeric layers may be configured such that the first object andthe second object may move within five feet of each other.

Energy is then absorbed by the elastomeric layers in the elastomericbearing (operation 1608). This absorption of energy is caused by thedeformation of the elastomeric layers and results in a reduction of thebending and torsional loads carried to the first and second objects.Heat is then released by the elastomeric layers (operation 1610) withthe process terminating thereafter. In this example, heat may bereleased as a result of the deformation of the elastomeric layers. Thequantity of heat may vary depending on the material properties and thelevel of deformation imposed on the elastomeric layers.

The flowcharts and block diagrams in the different depictedconfigurations illustrate the architecture, functionality, and operationof some possible implementations of apparatuses and methods in anillustrative configuration. In this regard, each block in the flowchartsor block diagrams may represent a module, a segment, a function, and/ora portion of an operation or step.

In some alternative implementations of an illustrative configuration,the function or functions noted in the blocks may occur out of the ordernoted in the figures. For example, in some cases, two blocks shown insuccession may be executed substantially concurrently, or the blocks maysometimes be performed in the reverse order, depending upon thefunctionality involved. Also, other blocks may be added in addition tothe illustrated blocks in a flowchart or block diagram.

Thus, the illustrative configurations provide a method and apparatus forreducing a force in exchange for a deflection. With the use of anillustrative configuration, two objects connected by a multi-directionaljoint assembly may move relative to each other. However, this movementis limited by the type of multi-directional joint selected and the layerconfiguration of the elastomeric bearing. As a result, the illustrativeconfigurations provide a stable joint that is rigid to normal forces butstill allows movement in bending and torsion of two objects relative toeach other within desired tolerances.

Moreover, because bending loads are typically the highest loads reactedby joints that separate objects, the load reduction afforded by thedeformation of the elastomeric bearing allows the structural elements atthe joint ends to be significantly reduced as compared to othercurrently used designs. In other words, because the deformation ofelastomeric layers within the elastomeric bearing absorb energy frombending and torsional forces, the total force reacted by the firstobject, second object, and third object becomes much less. As a result,fewer structural elements to carry the same initial load are required.Consequently, the structures required on either side of a joint systemconnecting two objects may be lighter and smaller.

Thus, with the use of an illustrative configuration, the load within asystem is reduced by allowing objects to move relative to each other incertain degrees of freedom as determined by the configuration of themulti-directional joint and damper.

The description of the different illustrative configurations has beenpresented for purposes of illustration and description, and is notintended to be exhaustive or limited to the configurations in the formdisclosed. Many modifications and variations will be apparent to thoseof ordinary skill in the art.

For example, the illustrative configurations may be implemented forother purposes other than maintaining distance between multiplehelicopters in load environment 100. For example, the differentillustrative configurations may be applied for use in an automobile,joints for robots, mechanical linkages, or any application in which acontrolled amount of relative movement between objects is desired.

Further, different illustrative configurations may provide differentfeatures as compared to other illustrative configurations. Theconfiguration or configurations selected are chosen and described inorder to best explain the principles of the configurations, thepractical application, and to enable others of ordinary skill in the artto understand the disclosure for various configurations with variousmodifications as are suited to the particular use contemplated.

What is claimed is:
 1. An apparatus comprising: a multi-directionaljoint assembly having a first end and a second end, wherein the firstend and the second end move relative to each other; and a damperassociated with the multi-directional joint assembly, wherein the damperis comprised of a number of elastomeric layers and a number of rigidlayers interspersed with each other.
 2. The apparatus of claim 1,wherein the damper is an elastomeric bearing.
 3. The apparatus of claim1, wherein the number of rigid layers and the number of elastomericlayers are associated with each other and the multi-directional jointassembly.
 4. The apparatus of claim 1, wherein the first end isconnected to a beam and the second end is connected to a rotorcraft. 5.The apparatus of claim 1, wherein the number of elastomeric layers iscomprised of a number of materials selected from at least one ofneoprene, rubber, an elastic polymer, a thermoplastic elastomer,synthetic polyisoprene, polybutadiene, ethylene-vinyl acetate, andchlorosulfonated polyethylene.
 6. The apparatus of claim 1, wherein thenumber of rigid layers is selected from at least one of a metal, aplastic, a polycarbonate, aluminum, steel, and titanium.
 7. Theapparatus of claim 1, wherein the damper absorbs energy from a number ofloads caused by at least one of a number of forces and a number ofmoments applied to at least one of the first end and the second end ofthe multi-directional joint assembly.
 8. The apparatus of claim 7,wherein the number of forces is selected from at least one of a normalforce, a torsional force, and a bending force, and wherein the number ofmoments is selected from one of torsion and a bending moment.
 9. Theapparatus of claim 1, wherein the multi-directional joint assemblyincludes a multi-directional joint comprised of a ball and a socket thatholds the ball, wherein the first end is associated with the ball, andthe second end is associated with the socket.
 10. The apparatus of claim9, wherein the damper is connected to the ball and the socket.
 11. Theapparatus of claim 10, wherein the multi-directional joint assemblyfurther comprises: an elongate member extending from the ball; and anenclosure associated with the elongate member having a cavity in whichthe ball, socket, and damper are located.
 12. The apparatus of claim 11,wherein the damper is directly connected to the enclosure and the socketand is indirectly connected to the ball by the enclosure and theelongate member.
 13. A multi-directional elastomeric dampened ball jointassembly comprising: a ball associated with a first end of themulti-directional elastomeric dampened ball joint assembly; a socketassociated with a second end of the multi-directional elastomericdampened ball joint assembly, wherein the ball is moveably held in acavity in the socket; and a hemispherical elastomeric bearing havingalternating rigid layers and elastomeric layers, wherein an outersurface of the hemispherical elastomeric bearing is associated with aninner surface of an enclosure, an inner surface of the hemisphericalelastomeric bearing is associated with an outer surface of the socket,and wherein the hemispherical elastomeric bearing absorbs energy andreduces at least one of a force and a moment applied to at least one ofthe first end and the second end.
 14. The multi-directional elastomericdampened ball joint assembly of claim 13, wherein the ball, the socket,and the hemispherical elastomeric bearing are located within an interiorof the enclosure.
 15. A method for reducing a force, the methodcomprising: receiving at least one of a number of forces and a number ofmoments applied to at least one of a first end and a second end of amulti-directional joint assembly, wherein the first end and the secondend move relative to each other; and deforming a number of elastomericlayers in a damper associated with the multi-directional joint assembly,wherein the damper comprises the number of elastomeric layers and anumber of rigid layers interspersed with each other.
 16. The method ofclaim 15 further comprising: absorbing energy from the at least one ofthe number of forces and the number of moments through the deformationof the number of elastomeric layers in the damper.
 17. The method ofclaim 15, wherein the number of forces is selected from at least one ofa normal force, a torsional force, and a bending force, and wherein thenumber of moments is selected from one of torsion and a bending moment.18. The method of claim 15, wherein the damper is an elastomericbearing.
 19. The method of claim 15, wherein the number of elastomericlayers is comprised of a number of materials selected from at least oneof neoprene, rubber, an elastic polymer, a thermoplastic elastomer,synthetic polyisoprene, polybutadiene, ethylene-vinyl acetate, andchlorosulfonated polyethylene.
 20. The method of claim 15, wherein thenumber of rigid layers is selected from at least one of a metal, aplastic, a polycarbonate, aluminum, steel, and titanium.